fix(sling): pass both feature and issue vars in formula-on-bead mode (#382)

When using `gt sling <formula> --on <bead>`, the code was only passing
the `feature` variable (set to bead title). This broke formulas that
expect `issue` (set to bead ID), like mol-polecat-work.

Now passes both common variables:
- feature: bead title (for shiny-style formulas)
- issue: bead ID (for mol-polecat-work-style formulas)

This allows either formula type to work with --on without requiring
the user to manually specify variables.

Fixes #355

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/sling.go

@@ -362,7 +362,7 @@ func runSling(cmd *cobra.Command, args []string) error {
 		if formulaName != "" {
 			fmt.Printf("Would instantiate formula %s:\n", formulaName)
 			fmt.Printf("  1. bd cook %s\n", formulaName)
-			fmt.Printf("  2. bd mol wisp %s --var feature=\"%s\"\n", formulaName, info.Title)
+			fmt.Printf("  2. bd mol wisp %s --var feature=\"%s\" --var issue=\"%s\"\n", formulaName, info.Title, beadID)
 			fmt.Printf("  3. bd mol bond <wisp-root> %s\n", beadID)
 			fmt.Printf("  4. bd update <compound-root> --status=hooked --assignee=%s\n", targetAgent)
 		} else {
@@ -398,9 +398,10 @@ func runSling(cmd *cobra.Command, args []string) error {
 			return fmt.Errorf("cooking formula %s: %w", formulaName, err)
 		}
 
-		// Step 2: Create wisp with feature variable from bead title
+		// Step 2: Create wisp with feature and issue variables from bead
 		featureVar := fmt.Sprintf("feature=%s", info.Title)
-		wispArgs := []string{"--no-daemon", "mol", "wisp", formulaName, "--var", featureVar, "--json"}
+		issueVar := fmt.Sprintf("issue=%s", beadID)
+		wispArgs := []string{"--no-daemon", "mol", "wisp", formulaName, "--var", featureVar, "--var", issueVar, "--json"}
 		wispCmd := exec.Command("bd", wispArgs...)
 		wispCmd.Dir = formulaWorkDir
 		wispCmd.Stderr = os.Stderr

internal/cmd/sling_test.go

@@ -345,6 +345,147 @@ exit 0
 	}
 }
 
+// TestSlingFormulaOnBeadPassesFeatureAndIssueVars verifies that when using
+// gt sling <formula> --on <bead>, both --var feature=<title> and --var issue=<beadID>
+// are passed to the bd mol wisp command.
+func TestSlingFormulaOnBeadPassesFeatureAndIssueVars(t *testing.T) {
+	townRoot := t.TempDir()
+
+	// Minimal workspace marker so workspace.FindFromCwd() succeeds.
+	if err := os.MkdirAll(filepath.Join(townRoot, "mayor", "rig"), 0755); err != nil {
+		t.Fatalf("mkdir mayor/rig: %v", err)
+	}
+
+	// Create a rig path that owns gt-* beads, and a routes.jsonl pointing to it.
+	rigDir := filepath.Join(townRoot, "gastown", "mayor", "rig")
+	if err := os.MkdirAll(filepath.Join(townRoot, ".beads"), 0755); err != nil {
+		t.Fatalf("mkdir .beads: %v", err)
+	}
+	if err := os.MkdirAll(rigDir, 0755); err != nil {
+		t.Fatalf("mkdir rigDir: %v", err)
+	}
+	routes := strings.Join([]string{
+		`{"prefix":"gt-","path":"gastown/mayor/rig"}`,
+		`{"prefix":"hq-","path":"."}`,
+		"",
+	}, "\n")
+	if err := os.WriteFile(filepath.Join(townRoot, ".beads", "routes.jsonl"), []byte(routes), 0644); err != nil {
+		t.Fatalf("write routes.jsonl: %v", err)
+	}
+
+	// Stub bd so we can observe the arguments passed to mol wisp.
+	binDir := filepath.Join(townRoot, "bin")
+	if err := os.MkdirAll(binDir, 0755); err != nil {
+		t.Fatalf("mkdir binDir: %v", err)
+	}
+	logPath := filepath.Join(townRoot, "bd.log")
+	bdPath := filepath.Join(binDir, "bd")
+	// The stub returns a specific title so we can verify it appears in --var feature=
+	bdScript := `#!/bin/sh
+set -e
+echo "ARGS:$*" >> "${BD_LOG}"
+if [ "$1" = "--no-daemon" ]; then
+  shift
+fi
+cmd="$1"
+shift || true
+case "$cmd" in
+  show)
+    echo '[{"title":"My Test Feature","status":"open","assignee":"","description":""}]'
+    ;;
+  formula)
+    # formula show <name> - must output something for verifyFormulaExists
+    echo '{"name":"mol-review"}'
+    exit 0
+    ;;
+  cook)
+    exit 0
+    ;;
+  mol)
+    sub="$1"
+    shift || true
+    case "$sub" in
+      wisp)
+        echo '{"new_epic_id":"gt-wisp-xyz"}'
+        ;;
+      bond)
+        echo '{"root_id":"gt-wisp-xyz"}'
+        ;;
+    esac
+    ;;
+esac
+exit 0
+`
+	if err := os.WriteFile(bdPath, []byte(bdScript), 0755); err != nil {
+		t.Fatalf("write bd stub: %v", err)
+	}
+
+	t.Setenv("BD_LOG", logPath)
+	t.Setenv("PATH", binDir+string(os.PathListSeparator)+os.Getenv("PATH"))
+	t.Setenv(EnvGTRole, "mayor")
+	t.Setenv("GT_POLECAT", "")
+	t.Setenv("GT_CREW", "")
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd: %v", err)
+	}
+	t.Cleanup(func() { _ = os.Chdir(cwd) })
+	if err := os.Chdir(filepath.Join(townRoot, "mayor", "rig")); err != nil {
+		t.Fatalf("chdir: %v", err)
+	}
+
+	// Ensure we don't leak global flag state across tests.
+	prevOn := slingOnTarget
+	prevVars := slingVars
+	prevDryRun := slingDryRun
+	prevNoConvoy := slingNoConvoy
+	t.Cleanup(func() {
+		slingOnTarget = prevOn
+		slingVars = prevVars
+		slingDryRun = prevDryRun
+		slingNoConvoy = prevNoConvoy
+	})
+
+	slingDryRun = false
+	slingNoConvoy = true
+	slingVars = nil
+	slingOnTarget = "gt-abc123"
+
+	if err := runSling(nil, []string{"mol-review"}); err != nil {
+		t.Fatalf("runSling: %v", err)
+	}
+
+	logBytes, err := os.ReadFile(logPath)
+	if err != nil {
+		t.Fatalf("read bd log: %v", err)
+	}
+
+	// Find the mol wisp command and verify both --var arguments
+	logLines := strings.Split(string(logBytes), "\n")
+	var wispLine string
+	for _, line := range logLines {
+		if strings.Contains(line, "mol wisp") {
+			wispLine = line
+			break
+		}
+	}
+
+	if wispLine == "" {
+		t.Fatalf("mol wisp command not found in log: %s", string(logBytes))
+	}
+
+	// Verify --var feature=<title> is present
+	if !strings.Contains(wispLine, "--var feature=My Test Feature") {
+		t.Errorf("mol wisp missing --var feature=<title>\ngot: %s", wispLine)
+	}
+
+	// Verify --var issue=<beadID> is present
+	if !strings.Contains(wispLine, "--var issue=gt-abc123") {
+		t.Errorf("mol wisp missing --var issue=<beadID>\ngot: %s", wispLine)
+	}
+}
+
 // TestVerifyBeadExistsAllowStale reproduces the bug in gtl-ncq where beads
 // visible via regular bd show fail with --no-daemon due to database sync issues.
 // The fix uses --allow-stale to skip the sync check for existence verification.